The present invention relates to a distributor type fuel injection pump for internal combustion engines, and more particularly to a device for reducing the combustion noise occurring during the idling operation of the engine (including a state approximate to the idling).
In fuel-injection type internal combustion engines including the Diesel engine, as well known it is necessary to control the fuel injection quantity in dependence on the operating conditions of the engine such as load or engine r.p.m. For this purpose, in a conventional fuel injection pump of said type only the injection quantity is controlled so that it increases or decreases in response to the engine operating conditions while the injection rate, i.e., the injection quantity dQ per unit time dT is kept constant. According to such controlling method, in order to obtain a decreased injection quantity during idling of the engine, it is so controlled that the effective stroke of the plunger of the pump is decreased so as to reduce the injection period, which results in an ignition lag in the cylinders of the engine, thus leading to sudden explosive combustion lasting for a short time and consequent knocking of the engine, with a resulting increased combustion noise peculiar to the idling of the engine. This noise phenomenon constitutes a public annoyance.